If your router is 192.168.0.1, then your reserved IP should be something in the router's DHCP pool, which is typically 192.168.0.2 - 192.168.0.254 (should be able to pick any of those in that range to reserve). If this is a cellular device, it may have a limited range of IP addresses, which I have seen is usually 10 devices, so it would be from 192.168.0.2 - 192.168.0.11 instead. Be mindful that if you reserve an IP address, no other device will be assigned that address and you may knock something else off of your network.
The default gateway should be your router's IP address (typically 192.168.0.1 for example). DNS is usually automatically assigned by your ISP, but you can also override that. Google's DNS servers are a good starting point and are 8.8.8.8 for DNS1 and 8.8.4.4 for DNS2. Hope that helps.
Remember Geejay is setting up a virtual network... so I think its best to give him the basics and let him learn to set up the basic DC, DNS, DHCP first, understand how the interact with each other, there purposes and how they actually work..
Then throw in 2/3 PCs into the network...
Once Geejay understands that he can relate it to a live environment